PROJECT SUMMARY Lymphatic filariasis (LF) is one of only a small number of diseases classified as potentially eradicable. In 1997, the World Health Assembly passed a resolution to eliminate LF as a public health problem and the approach involved yearly concurrent mass drug administration (MDA) to the at-risk population in 52 countries. According to the WHO, about 856 million people are at-risk of acquiring LF and need annual MDA treatment. After nearly 17 years of MDA to the at-risk population and spending several billion dollars, the incidence of LF infection has not significantly declined. This is likely due to subject non-compliance and lack of effectiveness of the drugs against the adult parasites living within the lymphatic system. Thus, reliance on the drug therapy approach alone is ineffective in limiting disease transmission. In fact, chemotherapy only treats current infections and does not prevent future re-infections leaving the patients susceptible to the disease. Several recent studies show that the disease is re- emerging in several parts of the world. Therefore, there is a critical need for developing an effective prophylactic vaccine that can support the current MDA approach for preventing disease transmission and total elimination of the disease from endemic regions. Unlike most other infectious organisms such as viruses, bacteria or protozoa, the lymphatic filarial parasites do not replicate within their definitive hosts. Therefore, the prophylactic vaccine against LF need not induce sterilizing immunity to be effective for controlling the infection. In fact, the World Health Organization (WHO) has determined that helminth vaccines that can prevent worm establishment by 50% will be effective in reducing overall morbidity and mortality. None of these candidates of the past two decades have advanced beyond rodent testing - partially because of poor protection and/or lack of resources to advance the technology. We have developed and established the first successful multivalent recombinant fusion protein vaccine (BmHAXT) for the prophylaxis of LF. The vaccine gives close to sterile immunity in rodents and significant protection in non-human primates (70%) when given along with the TLR4 agonist GLA-on-alum adjuvant. BmHAXT is now ready to move into the next phase of pre-clinical development as a tag-free, recombinant protein adjuvanted with the TLR4 agonist GLA on alum (LFguard?). Thus, the major focus of this project is to (Aim 1) develop a reliable, dependable, and consistent manufacturing process for the tag-free rBmHAXT+GLA/Alum vaccine formulation (LFguard?) that can be moved towards phase 1 human clinical trials and (Aim 2) to confirm that the newly developed LFguard? vaccine formulation has similar or greater prophylactic potential than the his-tagged BmHAXT research vaccine in experimental animal models.